Maybe there is a disconnect, I'm still trying to get my mind around everything. Would you mind taking a look at my detached tasks example? This represents my understanding of the proposal as it is right now. If Joe's instance-owned nursery existed I would have tried to use that instead and believe there would be a lot less boilerplate.
Regardless, I think it is important for an object to be able to create tasks that are working on its behalf without keeping it alive (and are indeed cancelled when the object goes away). If that isn't going to be possible then it isn't clear to me how efficient resource management is supposed to happen in this system. To be honest, I rarely encounter use cases where I want a task to keep an object alive. Usually when an object goes away that means there is no longer a demand for the work it represents and any tasks running on its behalf should be cancelled immediately.